[vtkusers] Clip Volume using freehand 2D Curve ROI

[Simon ESNEAULT]

Hello,

I don't think vtkImageTracerWidget will work on a Volume Rendering. The doc
says "3D widget for tracing on planar props".

I did exactly this, but the ugly way, using Qt to draw on top of the volume
rendering. The pipeline is as follow :

- Capture a screenshot of the current volume rendering (
using GetRenderWindow()->GetRGBACharPixelData( ... ) )
- Load a QPixmap of the screenshot on top the volume rendering's QVTKWidget
- Enable the user to draw using Qt's Scribble example :
http://doc.qt.io/qt-5/qtwidgets-widgets-scribble-example.html
- When the user has finished to draw, convert all points from
Qt coordinate system to VTK coordinate system.
- Generate a 3D conic-like mesh using the list of coordinate, the camera
position and direction in order to respect the perspective view (not that
easy ;) )
- Cap-Clip the mesh with the volume bounding box (
http://www.vtk.org/Wiki/VTK/Examples/Cxx/Meshes/CapClip )
- Generate a mask using vtkPolyDataToImageStencil
- Mask out the part that is below the free hand curve in the volume
( vtkImageMask or an equivalent )
- Remove the QPixmap to restore the volume rendering interaction ...

That is really ugly, and there might be a lot of better way to do this. But
the thing is : it just works ;-)

HTH
Simon


2016-03-30 15:54 GMT+02:00 longbowzhang <longbowzhangchina at gmail.com>:

> "freehand 2D curve": I think vtkImageTracerWidget will do the job.
> Together with vtkPolyDataToImageStencil, it is likely that you will get a
> stencil, which could be employed to clip the 3D volume.
>
> I am not sure whether this will finally work or not. But give it a try.
>
>
>
>
>
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Simon Esneault
Rennes, France
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